side lights intermittent fault

[Uncon]

I have a year 2000 R850GS. Last week the sidelights/running lights and tail light packed up on the way home. Got home on the headlight, pratted about with the fuses, found nothing wrong but the lights started working. Put the seat back on and they stopped. Pratted about with the switch and they started working, went to go for a test ride and they stopped... Tried pulling the switch apart to check that and it went ping all over the garage floor. Swore, then ordered another on fleabay. Used the V Stom the rest of the week. Today fitted switch and everything was fine, went to go out for a test ride and.... you guessed it....

I didn't attack the bike with a hammer but went in to make a cup of tea. There is obviously an intermittent fault with the sidelight circuit, the headlight always works fine except for initially with the new switch, moved the switch about a bit and it seems fine now. I'm assuming the 'new' switch is fine and there is nothing obviously wrong with the relevant fuse (no.2). Any thoughts on where to go next.

Thanks in anticipation!

 

[Stujw70]

Bad earth?
Check the various bits of wiring loom around the headstock as some of those can break down internally due to corrosion or just age.

You might need to take the tank off eventually to get good access to the looms either side of the head for a proper look.

 

[Steptoe]

The circuit wire in the ignition loom is broken. The sort section that runs from under the ignition barrel.

Wiggle the loom around and see if the side lights come on and off.

Cut the outer sheathing, find the break and repair.
Also cut the cable ties that hold the loom to the frame, they are part of the problem allowing the wiring to flex on the same small point everytime the bars are turned which leads to the wiring breaking after a few years.

 

[Uncon]

The good news is that the lights now work, the bad is that I didn't find a fault...

I wiggled the wires next to the ignition switch and got the classic 'now they work now they don't'. Good, looks like you were spot on. Pulled the switch apart (good tip about the tiny screw, never would have found that) stripped the wires and found nothing wrong. Pushed, pulled and wiggled each wire and nowt, the lights stayed on just fine. Taped it up, assembled it and went for a test ride, all good. Lights work fine. I'm guessing a bad solder? But the solders looked fine. The wires looked fine. It all looked fine.

I'm going to ignore it and wait till it goes wrong again, summer is coming so lights not quite as essential and I only work 12 miles away. But for future reference anyone know which colour wire works the side lights? An online search points me to the grey one?

Thanks for the help.